JPS59128756A - Low pressure mercury vapor discharge lamp for display device - Google Patents

Abstract

PURPOSE:To enable a sufficient luminous surface area to be secured by spreading electric discharge in a joint section connecting a pair of straight tubular sections by making the length of the joint section in direction intersecting a discharge path larger than the diameter of the straight tubular sections and coating the surface of the joint section facing the straight tubular sections with a phosphor film. CONSTITUTION:A discharge tube is made by fusing electrodes 4 and 4 to open ends of a pair of straight tubular sections 5 and 6 and connecting the other open ends with an almost semispherical joint section 7. The diameter (L) of the bottom area (8) of the joint section 7 is much larger than the diameter (l) of the straight tubular sections 5 and 6. The inner surface of the spherical area 12 of the joint section 7 is coated with a phosphor film 13 emitting red, green or blue monochromatic light.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a low-pressure mercury vapor discharge lamp used as a display element in a display screen installed in a baseball field or stadium or a display device showing road information. .

[Technical background of the invention and its problems]

Recently, television cameras and video cameras are being used at baseball fields and stadiums.
A display device is installed that projects and displays images stored in the TR on a large display screen. This device densely arranges thousands to tens of thousands of display elements on a display screen, and by selectively lighting up these display elements in accordance with image signals, a predetermined image can be displayed on the display screen. The image is now displayed.

Incidentally, currently known display elements of this type include those that emit light in a single color using an electron beam and those that emit light in a single color using a light bulb coated with translucent paint. However, although the electron beam has advantages such as being consuming, has low power, and has a long life, it has the disadvantage that the display element itself is expensive, resulting in high cost. Although light bulbs have the advantage that the light emitting element itself is inexpensive and the control circuit is simple, they also have the disadvantages of high power consumption and short lifespan.

Therefore, it is conceivable to use a low-pressure mercury vapor discharge lamp, typified by a fluorescent lamp, as another display element. It is well known that fluorescent lamps consume less power, have a long life, have high brightness, and are relatively inexpensive.From this point of view, it can be said that they fully meet the requirements for display elements. . However, since the arc tube of a fluorescent lamp is thinner than that of a light bulb or the like, it has not been put to practical use in a way that would provide a sufficient light emitting area when considering its use as a display element in the above-mentioned display device.

[Purpose of the invention]

The present invention was made based on these circumstances, and
The object of the present invention is to provide a low-pressure mercury vapor discharge lamp that can secure a sufficient light emitting area and can be used as a display element of the above-mentioned display device without any problems.

[Summary of the invention]

That is, in order to achieve the above object, the present invention includes a pair of straight pipe portions having electrodes sealed at one end and open at the other end;
A light-transmissive discharge tube is provided with a connecting portion that airtightly connects the other ends of these straight tube portions to form a substantially U-shaped discharge path between the electrodes, and the discharge tube is connected The length of the portion in the direction intersecting the discharge path is larger than the diameter of the straight tube portion, and the pair of straight tube portions are located inside the back surface of the connection portion, and at least one of the discharge tubes is The device is characterized in that a phosphor coating is applied to the surface of the connecting portion that faces the straight pipe portion to form a light-emitting surface.

[Embodiments of the invention]

The present invention will be explained below based on an embodiment shown in FIGS. 1 to 8.

FIG. 1 shows an outline of a large display screen installed in a corner of a baseball field or stadium, for example. The screen is approximately rectangular in shape and has several thousand to tens of thousands of display elements 2 and 1 on each screen.
...is densely arranged. These display elements 2 are low-pressure mercury vapor discharge lamps such as fluorescent lamps,
This structure is detailed in FIGS. 2 and onwards. That is, the discharge tube 3 is made of a translucent material such as glass. The discharge tube 3 has a pair of straight tube sections 5 and 6 having conventionally known electrodes 4 and 4 sealed at one end opening, and a substantially hemispherical shape connecting the other end openings of these straight tube sections 5 and 6. It consists of a connecting part 7. The bottom part 8 of the connecting part 2 has a substantially flat circular shape, and its diameter is equal to the diameter 5-! of the straight pipe parts 5 and 6. It is formed much larger than the. Two through holes 9, 9 are provided in the bottom part 8 at two places separated in the radial direction to communicate the inside and outside of the connecting part 7.
The openings at the other ends are butted against each other and are airtightly joined with glass. By this joining, a discharge tube 3 having a shape in which a pair of straight pipe parts 5 and 6 are led out in parallel in the axial direction from the bottom of the connecting part 7 is constructed, and a substantially U-shape is formed between the electrodes 4 and 4. A continuous discharge path 10 is formed.

The discharge path 10 has a circular passage cross section in the straight pipe parts 5 and 6, but the discharge space in the connecting part 7 is rapidly expanded according to the shape.
A pillar of sunlight passes through it. Further, on the inner surface of the spherical portion 12 of the connecting portion 7, that is, the surface facing the other end openings of the straight tube portions 5 and 6, a phosphor coating 13 that emits monochromatic light of red, green, or blue is provided. In addition, a transparent coating (not shown) for chromaticity correction is also coated on the outer surface. Therefore, the spherical part 12 of this connecting part 7 serves as a display part and forms a light emitting surface 14, and the pair of straight pipe parts 5.6 are positioned on the back side of this light emitting surface 14 and inside its outer periphery. has been done. The spherical portion 12 of this embodiment is curved with a curvature of 172 or more, where L is the diameter of the bottom portion 8.

Furthermore, a predetermined amount of mercury and a rare gas such as argon are sealed at a predetermined pressure in the discharge tube 3 having the above shape.

A lighting circuit (not shown) is connected to each of the discharge tubes 3, and by controlling these lighting circuits with an image control unit such as a microcomputer, the discharge tubes to emit light according to image signals are controlled. The number and position of 3... changes so that various images are displayed on one screen.

By the way, in the case of this type of display discharge tube 3, it is only the spherical section 12 to which the phosphor coating 13 is attached that contributes to light emission, so the discharge in the straight tube sections 5 and 6 is wasted. Therefore, the shorter the straight pipe section 5.6 is, the lower the weight and power consumption will be. However, in general, in a fluorescent rung, there is a region with low luminous efficiency called a Faraday dark region up to a certain distance (generally 30 degrees) from the electrodes 4, 4. The length from .4 to the other end opening is set to exceed the Faraday dark area, that is, 30 mm or more, so that the Faraday dark area does not enter into the connecting portion 7.

On the other hand, in the discharge tube 3 as described above, the light emitting surface 14
The maximum diameter of , that is, the diameter of the bottom part 8 of the connecting part 7 is 50
It is desirable to keep it below simple. That is, when a single discharge tube 3 is attached to the screen IJ-ngade 1 and lit, the maximum diameter L (ttan) of the light-emitting surface 14 and the visible distance (m) at which the shape of the light-emitting surface 14 can be determined are as follows. The relationship is as shown in FIG. Also, a large number of discharge tubes 3...
When displaying an image on the screen board 1 by arranging them closely on the screen board 1 and giving an image signal to the image control unit to light up the discharge tubes 3 at the necessary locations, the screen displays an image on the screen board 1. The maximum diameter L(w+) of the surfaces 14... and the distance (m) at which images can be distinguished have a relationship as shown in FIG. Considering the size of a typical baseball field or stadium, the visible distance of the light-emitting surface 14 is approximately 150 m at most, so as is clear from both figures above, the light-emitting surface 14...
It can be seen that a maximum diameter of 50 mm is sufficient.

Also, in the discharge tube 3 as described above, as in the case of a fluorescent lamp for general illumination, when the sealer increases the pressure of the filled gas, the positive column 11 in the discharge path 10 is constricted. Since the space is narrowed, the spread of light at the light emitting surface 14 is reduced. Conversely, if the pressure of the filled gas is lowered, problems such as early evaporation of the electron emitting material applied to the electrodes 4, 4 occur. Therefore, the present inventors determined the size of the spherical part 12 that contributes to light emission and the maximum distance of the discharge space in the direction perpendicular to the discharge path 10 in the spherical part 12 as D (van).
When the filled gas pressure was P (Torr), lighting experiments were conducted while varying the values of D and P, and the results shown in FIG. 8 were obtained. As is clear from Fig. 8, the value of D-P is 250 (Torr -tan).
It has been found that when the temperature is below p, the luminance of the light emitting surface 14 is particularly high, and the spread of light 9 becomes sufficient, so that the luminance distribution on the light emitting surface 14 becomes uniform. Therefore, it was concluded that in order to obtain preferable brightness and uniform brightness distribution as a display element, it is preferable to suppress the range of D-P≦250 Torr-m.

According to such a configuration, when a discharge occurs between the electrodes 4 and 4, ultraviolet rays are emitted from the positive column 1 that passes through the U-shaped discharge path 1o, and in the process of passing through the connecting portion 7, the ultraviolet rays are The light enters the phosphor coating 13 on the inner surface of the spherical section 12 and excites the phosphor, so that visible light is emitted from the entire surface of the light emitting surface 14 of the spherical section 12. In this connecting portion 7, the discharge path 1
Since the discharge space is expanded by forming a circular shape whose length in the direction perpendicular to 0 is longer than the diameter of the straight pipe section 5. can get.

Moreover, as in this embodiment, the relationship between the filled gas pressure P and the maximum distance of the discharge space of the sphere 10-surface portion 12 that contributes to light emission is set to D-P≦25.
If it is defined as 0 Torr-trm, the beam of sunlight passing through the connecting portion 7 will be sufficiently spread, and there will be no risk of early evaporation of the electron radioactive material applied to the electrode 4.4, making it optimal as a display element. .

Furthermore, since the straight pipe parts 5 and 6 are located on the back surface of the light emitting surface 14 and inside the outer periphery thereof, these straight pipe parts 5 and 6
are covered by the light emitting surface 14 when viewed from the direction of the light emitting surface 14, that is, from the display direction, and therefore a large number of discharge tubes 2
When the discharge tubes 2 are arranged with their light emitting surfaces 14 facing in the same direction, the discharge tubes 2 can be closely arranged on the screen door 1.

In the above-described embodiment, the planar shape of the connecting portion 21 is circular, but the planar shape of the connecting portion 21 may be a circular shape as shown in FIG. 9, or a polygonal shape as shown in FIG. It may be used as a connecting portion 3.

Also, the bottom does not necessarily have to be flat.

〔Effect of the invention〕

According to the present invention described in detail above, a pair of straight pipe parts are connected to each other by a connecting part to form a substantially U-shaped discharge path between the electrodes, and the length of the connecting part in the direction intersecting the discharge path is The diameter of the straight pipe portion is larger than the diameter of the straight pipe portion, and the pair of straight pipe portions are located inside the back surface of the connecting portion, and a phosphor coating is provided on at least the surface of the connecting portion facing the straight pipe portion. As a result of the coating, the discharge spreads widely at the connecting part, so a sufficient light emitting area can be secured, and therefore it can be used for display devices in the same way as conventional electron beams and light bulbs. In addition, since the straight tube part is hidden behind the light emitting surface, the straight tube part does not get in the way when many discharge tubes are lined up with their light emitting surfaces facing the same direction, and these discharge tubes can be lined up closely. There are advantages that can be achieved.

[Brief explanation of the drawing]

1 to 8 show an embodiment of the present invention, in which FIG. 1 is a schematic diagram of a display screen, FIG. 2 is a perspective view of a discharge lamp, FIG. 3 is a bottom view, and FIG. 4 is a diagram of a discharge lamp. 3 is a sectional view taken along line IV-M, FIG. 5 is a sectional view taken along line V-V in FIG. 3, and FIGS. 6 and 7 are characteristics showing the relationship between the diameter of the light emitting surface and the visible distance. 8 are characteristic diagrams showing the relationship between the enclosed rare gas pressure and the maximum discharge space distance of the connecting portion, and FIGS. 9 and 10 are plan views showing modified examples of the connecting portion, respectively. 3...Discharge tube, 4...Electrode, 5, 6...Straight tube part,
7゜21.31... Connection part, 10... Discharge path, 13
... Phosphor coating, 14... Light emitting surface. Applicant's agent Patent attorney Takehiko Suzue 13-

Claims (3)

[Claims] (1) One end with an electrode sealed and the other end open.
A light-transmissive discharge tube is constructed of a pair of straight tube sections and a connecting section that airtightly connects the other ends of these straight tube sections to form a substantially U-shaped discharge path between the electrodes. The connecting portion of the discharge tube has a length in a direction intersecting the discharge path that is larger than the diameter of the straight tube portion, and the pair of straight tube portions are located inside the back surface of the connecting portion. In addition, a low-pressure mercury vapor discharge lamp for a display device, characterized in that a phosphor coating is applied to at least the surface of the discharge tube facing the straight tube portion in the connecting portion to serve as a light-emitting surface. (2) The maximum distance of the discharge space in the direction intersecting the discharge path in the connection part is n (tm), and the pressure of the enclosed rare gas is P(
The low-pressure mercury vapor discharge lamp for a display element according to claim (1), characterized in that when D-P≦250 (Torr-m). (3) Claims (1) or (2) characterized in that the length from the electrode to the connecting portion in the straight pipe section is formed to be longer than the Faraday dark area.
) A low-pressure mercury vapor discharge lamp for display elements as described in item 2.